1. Field of the Invention
The invention relates to vehicle trailers and in particular to frame-type vehicle trailers. More particularly, the invention is directed to a frame-type vehicle trailer which includes a pair of generally triangular-shaped members which form an assembly with a single cross member thereby eliminating a plurality of frame cross members, for more securely and efficiently supporting suspension assemblies suspended therefrom.
2. Background Art
Vehicle trailer frames and the axle/suspension systems suspended therefrom, including trailer frames for vans, reefers, tankers, dumps, lowbeds, flatbeds, platforms, and logging trailers, must be capable of reacting to roll moments, side loads, brake loads and other forces in order to safely and efficiently transport payloads or cargo. Since such forces act through the axle/suspension systems of the trailer, mounting of the axle/suspension systems to the trailer frame is of critical importance.
Flatbed and platform trailers in particular, due to their lack of a stiff upper structure and/or heavy duty characteristics such as is found in the other above-described types of vehicle trailers, are subject to greater deflections under load which can cause stress at rigid areas of the trailer. More specifically, such rigid areas are created by the trailer frame cross member/suspension assembly mounts. More particularly, a typical flatbed or platform structure typically consists of a pair of longitudinally extending, spaced-apart parallel main members, which are interconnected by three perpendicularly extending cross members for each axle/suspension system suspended from the trailer frame. The cross members typically are welded to the main members to form an integral rigid ladder-like trailer frame structure. A plurality of web stiffeners also are conventionally added to stabilize the relatively tall thin web of each main member, which usually is an I-beam, thus adding additional rigidity to the trailer frame structure.
Such a conventional flatbed or platform trailer assembly as described immediately above, while having years of utility in the field, fails to operate optimally for various reasons. More particularly, these types of trailer assemblies, although having certain rigid areas as noted hereinabove, generally display relatively flexible structures. For example, when such a trailer frame is subjected to lateral loads resulting from a sharp turn, the ladder-like structure of the frame deflects into a parallelogram-like structure. More specifically, these lateral loads actually combine with vertical, longitudinal and roll loads to produce a twisted parallelogram structure. In such a relatively flexible structure, the trailer frame main members and cross members actually distort into S-shaped structures. However, at the certain rigid areas of the trailer frame, namely, the interconnection areas of the cross members to the main members, the trailer frame is prevented from distorting resulting in high stress at such interconnections.
Aggravating the above-described prior art problem are the discontinuities in frame structure and interruptions of welds caused by the non-corresponding size of the suspension assembly hangers and the frame main members. More particularly, the hanger for each of the pair of suspension assemblies of each axle/suspension system typically is wider than the bottom flange of the respective main member I-beam from which each hanger depends. This extra width of each hanger relative to the bottom flange of its respective I-beam typically extends inboardly from the I-beams. So that the cross members disposed above the hangers can contact the upper surface of the hangers yet still nest in the I-beams to form a rigid mount for the suspension assemblies, the ends of each cross member are notched or coped out around the bottom flange of each I-beam. Alternatively, a spacer is used to fill the gap between the inboardly extending additional width of each hanger and the bottom surface of the cross members. In either case, the welds securing each hanger to the trailer frame structure must be interrupted at the junction of the bottom flange of the I-beam and the cross members or the spacer.
The above-described interrupted welds combined with the high stress inflicted on the rigid connection area of the cross members to the main members can result in cracks in the trailer frame main members or cross members, or in the welds at the nesting junction of each of the cross member ends in the web of its respective I-beam main member. Cracks further can occur in welds at the interface of each end of the cross members to its respective hanger or the air-spring mounting plate.
Moreover, assembly of a prior art trailer frame, including suspension assembly mounts, during manufacture of the vehicle trailer is difficult, time consuming, labor intensive, and requires a certain level of skill and training. There are typically about thirty (30) component parts needed to mount a single axle/suspension system, which are expensive to produce and inventory. In addition, the weight of those approximately thirty (30) component parts can total about three hundred fifty (350) pounds.
The above-described problems associated with conventional or prior art vehicle trailer frames are overcome by the trailer frame cross member/suspension assembly mount of the present invention. The present invention improves support against the twisting, parallelogram and S-shaped deflections typically caused by vertical, lateral, longitudinal, and roll loading, by replacing a plurality of cross members with a cross member/suspension assembly mount comprising a single cross member having a generally triangular-shaped structure attached to each of its ends, and also provides for an easy to assemble, simple and lightweight structure.